The present invention relates to a method for the end-surface connection of a carrier matrix of a honeycomb body, in particular a catalyst carrier body, through the use of a joining technique. The matrix is disposed in a tubular jacket and is laminated and/or wound from at least partially structured sheet metal foils or layers. The invention also relates to an apparatus, in particular for carrying out the method.
Known honeycomb bodies, in particular metallic catalyst carrier bodies, include a carrier matrix with, for example, spirally wound, very thin-walled, smooth and/or corrugated sheet metal foils or layers. The layers are interconnected in a circular-cylindrical or oval-cylindrical tubular jacket through the use of a joining technique, by welding, brazing, sintering, adhesive bonding or the like.
In order to increase the resistance of such a honeycomb body to thermal alternating loads, it is already known to connect the sheets of the carrier matrix to one another, and if appropriate to the tubular jacket, through the use of a joining technique, only in certain subregions, for example at end surfaces. That is done so that under thermal loading there are possibilities for the tubular jacket and the carrier matrix to expand unhindered, thereby avoiding plastic deformations of matrix cells under alternating load, with the consequences of delamination and destruction of the carrier matrix.
Classic methods for the end-surface connection of a carrier matrix of a honeycomb body, in particular a catalyst carrier body, through the use of a joining technique, wherein the matrix is disposed in a tubular jacket and is laminated and/or wound from at least partially structured sheet metal fails or layers, are nowadays carried out in particular in a discontinuous process, lasting several hours, in a high-temperature oven. In that case, the individual honeycomb bodies are loaded into the oven by being collected together in batches. In order to avoid chemical reactions, such as undesired crystal formation or oxidation, in particular on the surface of the sheet metal foils or layers, the joining process takes place in an oven under an inert gas atmosphere, for example containing argon and/or hydrogen, or in a vacuum. Consequently, the joining process in particular entails quite high expenditures for apparatus and corresponding costs.
It is accordingly an object of the invention to provide a method and an apparatus for the end-surface connection of a carrier matrix of a honeycomb body by a joining technique, which overcome the hereinafore-mentioned disadvantages of the heretofore-known methods and apparatuses of this general type in which, in particular, the method is significantly shortened, the carrier matrix is a catalyst carrier body and the matrix is disposed in a tubular jacket and is laminated and/or wound from at least partially structured sheet metal foils or layers.
With the foregoing and other objects in view there is provided, in accordance with the invention, a method for the end-surface connection of a carrier matrix of a honeycomb body, in particular a catalyst carrier body, by a joining technique. The method comprises providing the honeycomb body with at least one end surface and providing the carrier matrix with laminated and/or wound at least partially structured sheet metal layers disposed in a tubular jacket. The at least one end surface of the honeycomb body is at least partially heated with a surface inductor having appropriately disposed induction coils, to produce interconnections of the sheet metal layers at least at locations, in particular at spots. At least one of the surface inductor and the honeycomb body are moved relative to each other during the heating step, in particular by rotating.
With the objects of the invention in view, there is also provided, in combination with a honeycomb body, in particular a catalyst carrier body, including at least one end surface and a carrier matrix disposed in a tubular jacket and having laminated and/or wound at least partially structured sheet metal layers, an apparatus for carrying out an end-surface connection of the carrier matrix by a joining technique. The apparatus comprises a surface inductor having induction coils. The induction coils at least partially heat the at least one end surface to produce interconnections of the sheet metal layers at least at locations, in particular at spots.
As is mentioned, for example, in European Patent Application 0 245 737 A1, corresponding to U.S. Pat. Nos. 4,832,998; 4,803,189; 4,946,822; and 4,923,109, the use of inductive measures for at least partial connection of a laminated and/or wound carrier matrix of a honeycomb body through the use of a joining technique, has previously scarcely been considered.
That is because it was assumed that, in contrast with the tubular jacket, the honeycomb structure taken as a whole could only be very poorly heated up and brought to a high enough temperature for connection by a joining technique, both through the use of induction coils and by thermal irradiation from outside.
However, the present invention surprisingly makes it possible in an advantageous way for at least one end surface of the carrier matrix of a honeycomb body to be connected by a joining technique in a matter of seconds. In general, it is possible in this case to dispense with inertizing measures, since chemical reactions do not occur for a sustained period of time, at least insofar as slowly proceeding equilibrium reactions are concerned, due to the extremely reduced connecting time.
In accordance with another mode of the invention, for application of the invention in the production of particularly flexible catalyst carrier bodies, it is proposed that the connecting locations on the end surface of the honeycomb body preferably be established in a locally selective way and/or variably with regard to their extent on the end surface. A surface inductor which is variable in an advantageous way with regard to the production of connecting locations and/or connecting spots, that is with regard to its effective regions, is proposed for this purpose.
In accordance with a further mode of the invention, the invention may be combined with possibly already existing inductive apparatuses for the at least partial connection of the ends of sheet metal foils or layers to a tubular jacket, especially through the use of a joining technique. Therefore, it is proposed, for example, to construct the induction coils in such a way that the end surfaces of the honeycomb body are heated up in such a manner that no connections of the sheet metal foils or layers to the tubular jacket are established.
In accordance with an added mode of the invention, an alternative embodiment thereto provides, for example, for constructing the induction coils at least partially in such a way that the end surface of the honeycomb body is heated up in such a manner that connections of the sheet metal foils or layers to the tubular jacket are established at the same time.
In accordance with an additional mode of the invention, the induction coils are constructed in such a way that essentially the entire end surface of the carrier matrix of the honeycomb body can be heated up, in particular uniformly.
In accordance with yet another mode of the invention, this can also be achieved and/or supported, for example, by moving, in particular rotating, the surface inductor and/or the honeycomb body relative to each other.
In accordance with yet a further mode of the invention, as an alternative or in addition thereto, the surface inductor may also be appropriately constructed, for example with segmented induction coils or as a so-called spiral inductor.
Tests have shown that the induction coils of an apparatus according to the invention do not have to be operated with a high AC voltage frequency of approximately 3 MHz, as may be expected on the basis of theoretical considerations. On the contrary, in accordance with yet an added mode of the invention, a much lower AC voltage frequency of approximately 138 to 170 kHz, in particular approximately 140 to 160 kHz, preferably approximately 150 kHz, is already adequate to introduce sufficient energy into the sheet metal foils or layers to be able to establish the connection through the use of a joining technique as is described below, for example.
In accordance with yet an additional mode of the invention, the method is suitable, in particular, for connections made by joining techniques such as brazing or sintering. The joining techniques can be applied in an advantageous way while the process of producing catalyst carrier bodies is in progress, without exceeding the short cycle times for the remaining production steps for the connecting operation.
Finally, it should also be mentioned that not only can the features described above be combined with one another but they can also be combined with known types of connections produced through the use of joining techniques. In particular, in accordance with a concomitant mode of the invention, the advantages of the present invention can be combined with the advantages of the production of catalyst carrier bodies under an inert gas atmosphere or some other defined atmosphere for surface treatment, in that the honeycomb body is kept entirely or partly under inert gas during the connecting operation.
Other features which are considered as characteristic for the invention are set forth in the appended claims.
Although the invention is illustrated and described herein as embodied in a method and an apparatus for the end-surface connection of a carrier matrix of a honeycomb body by a joining technique, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.
The construction and method of operation of the invention, however, together with additional objects and advantages thereof will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.